Cycasin, the glucoside of methylazoxymethanol (MAM), and MAM-glucuronide are colon carcinogens when orally administered to rats. Both compounds are hydrolyzed by appropriate bacterial enzymes to yield the common aglycone, MAM, the proximate carcinogen. It would be expected that since the same product, MAM, is generated in the intestinal tract when the two compounds are administered the end carcinogenic effects would be similar. However, MAM-glucuronide appears to be a better colon carcinogen than cycasin, which is better liver and kidney than colon carcinogen. Why the conversion of the primary alcohol group of cycasin to a carboxylic acid group increases the effectiveness of the compound as a colon carcinogen is being investigated. The colon carcinogen MAM when injected into rats and MAM formed from the oxidation of injected dimethylhydrazine and azoxymethane do not form the glucoronide and is not excreted with the bile. Injected MAM must get to the colon lumen via another route. Radioisotope labeled MAM will be used to determine whether or not radioactivity can be found in the colon mucosa after injection of labeled MAM.